The present invention relates to the field of needled textile structures and it relates more particularly to a system for presenting a pre-needled textile sheet automatically at the inlet of a cross-layer.
In traditional industrial needling processes, the textile sheet for needling and that is to be used, for example, in making protective parts for use in high temperatures, is built up from a plurality of tows placed side by side and each comprising a multitude of textile yarns, advantageously of the monofilament type. This first textile sheet is generally needled briefly a first time in a pre-needling module and is then directed to a transverse inlet of a cross-layer whose longitudinal inlet receives a second textile sheet that is generally pre-needled in similar manner and that is to serve as a support onto which the pre-needled first textile sheet is to be deposited. Nevertheless, proper cross-laying assumes that the first textile sheet arrives with constant width and position that are determined with very great accuracy.
Unfortunately, at present, presentation to the transverse inlet of a cross-layer is provided solely in manual manner by an operator who constantly watches the first textile sheet and, whenever possible, modifies the position and the width thereof manually so as to ensure that the sheet is properly covered, thereby limiting defects in the final textile structure. Unfortunately, when too many defects appear, the industrial process must be interrupted with the grave consequences that stem therefrom. In particular, this method is particularly expensive in labor costs (especially when a process is run continuously 24 hours a day), and it is not free from defects due to the presence of the human factor.
The present invention mitigates these drawbacks by providing apparatus for automatically presenting a generally pre-needled textile sheet from an upstream module to feed a cross-layer module, the apparatus comprising means for measuring the positions of the longitudinal edges of said textile sheet, means for adjusting the width of said textile sheet, means for adjusting the position of said textile sheet, and processor means for responding to said position measuring means to control said adjustment means in real time in such a manner that said textile sheet presents determined width and position.
With this particular configuration, it is possible automatically to obtain accurate centering of the textile sheet coming from a tow feed module or a pre-needling module and for the width and the position of the sheet at the inlet of the cross-layer to be constant in a manner that is accurately guaranteed and controlled in real time so as to ensure accurate overlapping in the final textile structure.
Advantageously, the means for measuring the positions of the longitudinal edges of the textile sheet comprise at least one detector (and preferably two detectors each disposed in register with a corresponding edge of said textile sheet), and preferably a linear optical sensor made up of a plurality of light-emitting diodes (LEDs) disposed in register with a plurality of light-receiving diodes, and with the textile sheet to be measured passing between them. Alternatively, these measuring means can be constituted by a digital camera placed above the textile sheet. Similarly, the means for adjusting the width of the textile sheet comprise a curved adjustment bar which can be pivoted about a pivot axis under the control of a lever arm by means of a first actuator which modifies the position of the curvature of the central portion of the adjustment bar, thereby acting on the width of the textile sheet passing over said curved adjustment bar.
In similar manner, the means for adjusting the position of the textile sheet comprise a second actuator acting on a support frame for the textile sheet so as to move it relative to the structure of the apparatus. The first and second actuators are preferably electrically controlled actuators that are actuated directly by said processor means.
The processor means comprise a digital computer or a programmable controller responsive to said measurements taken by said position detectors to control said first and second actuators for adjusting the width and the position of said textile sheet so as to provide real time regulation of its width and position relative to predetermined reference values previously supplied to said processor means by an operator. Advantageously, the predetermined reference values comprise the total width for the sheet Nc and the position of a longitudinal central axis of the sheet Pc.
The invention also provides a method of automatically presenting a textile sheet that is implemented in the above apparatus.